Global temperature rises may seem gradual, but the changes they bring can be sudden, widespread and self-reinforcing. Scientists call these changes turning points. When a tipping point is reached, the Earth's system changes abruptly and dramatically, often irreversibly, like the Amazon rainforest. turning into savannah – a point of no return that already exists dangerously close.
But today, a group of 160 scientists from 23 countries announces that the planet has already reached its first major tipping point: the widespread loss of warm-water coral reefs. This is due, first of all, to the rapid increase in sea temperature – the seas have absorbed 90 percent excess heat we created, but also acidification, which occurs due to more atmospheric CO2 interacting with water. (This prevents corals from building the protective skeletons that form the complex reef structure.) Ocean surface warming has quadrupled since the late 1980s. Accordingly, half of the world's coral cover has disappeared over the past half century.
“We're no longer talking about future tipping points – one is happening right now,” Steve Smith, a research fellow at the University of Exeter's Global Systems Institute and co-author of the report, told Grist. “While our governments are used to planning for gradual, slow changes, it appears that things are really accelerating.”
The more individual corals die, the harder it is for the reef to bounce back, destabilizing it and pushing it into a spiral of extinction. A quarter of all marine species depend on these vibrant warm-water ecosystems, which cover about 350,000 square miles, but corals are bleaching as they secrete the symbiotic algae they need to harvest energy. Since 2023, more than 80 percent of the world's reefs have suffered the largest and most intense bleaching events on record. The ever-increasing acidity makes it even more difficult for corals to reproduce and subsequently grow as a result of this type of disturbance.
Warm-water corals are particularly vulnerable to climate change because they have made an evolutionary trade-off. Being close to the ocean's surface, their symbiotic algae absorb abundant sunlight to provide themselves with energy, meaning they don't need to rely as heavily on external nutrients. But this arrangement also means that during marine heat waves, hot water envelops the corals, stressing them to the point that they release their algae, causing bleaching.
“It's a compromise. They need to find a balance,” said Gordon Zhang, a senior scientist with the Reef Solutions group at Woods Hole Oceanographic Institution, who was not involved in the new report. “If the water isn't moving much and the area is very shallow, the water just continues to heat up.”
In addition to their critical role in supporting marine life, these reefs provide $9.9 trillion worth of goods and services annually, such as fisheries and tourism, supporting the livelihoods of 1 billion people. They also act as giant barriers for coastal communities, absorbing the impact of storm surge, the walls of water that hurricanes wash ashore: reefs in Mexico, for example, reduced damage from Hurricane Dean in 2007. by 43 percent.
Thus, coral reefs are important both ecologically and economically, but civilization is completely unprepared for them to reach this tipping point, let alone other impending tipping points such as glacial retreat. “We are now in a new reality, and we can no longer rely on the institutions and policies designed for the old,” said Manyana Milkoreit, who researches global governance at the University of Oslo and co-authored the report, during a press conference announcing the findings.
First, countries as a whole are not nearly ambitious enough in reducing greenhouse gas emissions, which are putting unprecedented pressure on coral reefs and other important systems. Second, some tipping points may be so catastrophic that governments will struggle to cope with the societal-shattering consequences. Changes in ocean currents in the AtlanticFor example, Europe will be plunged into deep frosts and monsoon rains, which distant countries need to grow crops. And third, these irreversible changes could intensify and worsen other crises—droughts would get worse, for example, if the Amazon turned into savannah—a very undesirable kind of synergy.
Essentially, people need to actively prevent tipping points because once they start, there is no going back. Coral ecosystems will not be able to recover and stabilize if we continue to warm and acidify the oceans. “The key message here is: don’t think we already know what to do or that we’re already doing everything we can,” Milkorate said. “It’s not just more of the same old or a matter of implementing existing policies—it requires a different approach to governance.”
But when it comes to society's response to these risks, the report's authors actually see a positive inflection point in the price of renewable energy technologies like wind and solar, and the batteries needed to store that energy. there were cratersmaking these cleaner options more cost effective than developing fossil fuel infrastructure. Texas, for example, produces much more combined wind and solar energy than any other state – in 2023, a third of its electricity came from renewable energy – not because its Republican leadership is fanatical about clean energy, but because it is good business. However, the market can only capsize so quickly as the world is on track to meet the Paris Agreement goal of limiting warming to well below 1.5 degrees Celsius.
At the local level, scientists and policymakers can buy time for coral reefs. For example, turning them into marine protected areas preserves biodiversity and helps maintain the stability of these ecosystems. More greedy control of overfishing prevents declines in fish populations. And reducing coastal pollution from agriculture and sewage eliminates stressors that only worsen the condition of reefs.
The healthier the reef, the better it can withstand the weather. climate shocks such as marine heatwaveswhich will only become more widespread and intense from here on out. “Like most natural systems, corals can be resilient—they can bounce back, but only a certain number of times,” Mike Barrett, chief scientific adviser to the World Wildlife Fund in the United Kingdom, which funded and co-authored the report, said during a press conference. “What we've done is just pushed them beyond what they can handle.”
That's why scientists are actively rescuing corals, bringing them to laboratories and learning to breed these extremely sensitive animals. By establishing populations in a controlled environment, they can learn the basic science of coral biology and reproduction, and how species respond to different conditions. If a certain part of the ocean becomes inhospitable to corals, researchers could keep the species in captivity and even reintroduce them into the wild if temperatures drop again.
Even in the near future, they could breed healthier, more genetically diverse coral babies that are more tolerant of heat, and then return them to the wild. “Corals are increasingly being brought into human care, both as a Noah’s Ark and as a genetic refuge,” said Rebecca Albright, director Coral Regeneration Laboratory at the California Academy of Sciences, who were not involved in the new report. “As ecosystem degradation intensifies and the situation continues to deteriorate, usually management moves to a more risk-taking approach, where you are willing to try more things.”
Yes, the tipping point may be a metaphorical cliff, but all is not lost for the world's corals—if humanity accelerates the transition to clean energy. “The race is on to transform society's entire energy base within a generation – something that has never been done before – away from fossil fuels and overexploitation towards a cleaner, safer future over time to avoid further tipping points and the devastating consequences they will bring.”
